All of our work is NTSC Apple Prores 422 (29.97)
and our audio is at 48k 16 bit (and perhaps 24bit, don't know if that matters...)

The issue I'm having is when editing precise cuts on the timeline, I get random sync on playback (on the canvas, not the client monitor). Sometimes is 4 frames out of sync sometimes 2, and sometimes it plays correct. It's not a drifting issue though, it just starts the playback off sync, you stop go back play again, and it will start right on, and so on, very random.

Our editors are even resorting to exporting qt's to make sure the cuts right. I have replaced the house sync (even put a machine on a black burst generator by itself), and the problem persists. Reformatted and reinstalled software, changed drivers for lhi, placed the media in a local drive,and even went back to 10.5 instead of 10.6 to no avail.

If I remove the LHi drivers, the system is dead on. No sync issues at all, yet AJA is telling me that it's the first they hear (and they've been very curious about the problem).

I am wondering if anyone else running a similar setup was experiencing the same "looseness" editing. Obviously suggestions on what to fix/troubleshoot are also welcome.